Mr. Shanshiry
Aiki is a result of manipulating energy between two people- from tempering and changing your body from within. It is an old concept that existed in India, China and in Japan. The easiest way to conceptualize it is to imagine that someone could have trained their body to remain in balance with contradicting forces held within it, through the use of bone and tendon and fascia more than muscle and that your breath could be trained to enhance that sense of being suspended in balance. Now imagine that someone pushing or pulling on you doesn't really feel like much to you but they have to exert a lot of effort to get nowhere. Now imagine your body were so connected that were you to move even a small amount the power differential between you and other normally trained people was so overwhelming that they felt they were either magnetically drawn to you by their grip or they were manipulated and thrown or locked. Now add waza to that equation.
While it is defined by different "ways" to use it, different arts and their techniques etc. Teachers and students alike from traditional arts like Aikido, Daito ryu, Taiji, Bagua, are noting that for some strange reason it feels like the best in their arts. Others of a more aggressive breed; Judo, MMA, BJJ are noting it is very practical and powerful in freestyle grappling-if you meet someone who knows how to use it in that venue...not everyone does!
Of course it is far more complicated than that but hopefully it helps paint a picture
Cheers
Dan